This invention relates to containers; the body for such containers being in the form of cylindrical one-piece metal can having an open end terminating in an outwardly directed peripheral flange merging with a circumferentially-extending neck portion (the can body being hereinafter referred to as a D&I can). Methods of forming said neck and flange in a D&I can body and to apparatus for forming the said peripheral flange and neck portion.
The background for this disclosure relates to the way in which D&I can bodies are manufactured in drawing and then multiple ironing operations. For 20 years beverage containers have been made by a drawing and then multiple ironing processes in which the metal material is first drawn into a cup to establish the shape and a basic inside diameter and the cup is then pushed through a series of ironing rings which merely thin the side wall and do not appreciably affect the diameter.
The cross-sectional configuration of the ironing ring includes a chamfer, a land and finally a relief angle. The ironing process begins on the chamfer and is completed by the land during which time no drawing takes place. The process is done at high speed under a coolant/lubricant flood in order to accommodate the severity of the operation especially the heat. These containers have to be washed and in some cases chemically treated to remove residual lubricant and improve corrosion performance of organic coatings and decoration subsequently applied to the container. Coatings are normally applied after the shell has been trimmed and washed free of lubricants and metal fines.
The ironing steps result from the difference between the clearance between a punch and ironing ring land and the thickness of the metal sidewall. That clearance represents the amount to which the side wall of the container will be thinned. Usually, metal with no organic coating passes through three different ironing rings in a D&I operation during which ETP electrolytic of T-1 to T-5 temper tinplate or H19 aluminum container sidewall is reduced about 25% in the first pass, about 25% of its new thickness in the second pass, and about 40% of its new thickness in the last pass, while the metal and tooling are flooded with lubricant coolant.
This operation increases the side wall length to several times that of the cup which was formed in an ordinary and separate one or two-draw operation. The cleaned and trimmed D&I can may then be necked and flanged in a separate apparatus and an independent operation. The grain orientation of the ironed sidewall is highly directional and the D&I can is subject to longitudinal cracking particularly at the radially extending flange. The purpose of the peripheral flange is usually to provide an element to which a can end is secured after the can has been filled, this securing being done by deforming the end flange of the can body together with a peripheral cover hook of the can end so as to form a double seam. Consequently, flange cracks are a problem to achieving a hermetic double seam. The neck enables the flange, and therefore the can end, to be of smaller diameter than if there were no neck; usually the radial depth of the neck is such that the double seam has an external diameter less than that of the cylindrical side wall. Necking also minimizes the radial extent of the flange thus helping to resist flange cracking.
In some types of metal lids, such as those having easily opened ends of the so-called "ring pull" or "tab" type, the end to be seamed on to the flange of the can body is preformed with the scored opening feature. These opening features often determine the diameter of the end and only recently has the tab-type been reduced in size to permit ends as small as 202 being 2 and 2/16" across the double seam (can makers conventional terminology).
The end neck may serve another purpose, which is to provide a convenient means whereby a carrier can engage the container; such carriers are designed to hold a plurality of containers and may be of, for example, paperboard or a flexible plastic material. The type of carrier which engages the neck of a container of the kind with which this disclosure is concerned may include a horizontal web in which there are a plurality of holes, the periphery of each hole engaging below the above-mentioned container double end seam so as to support the container wholly or partly thereby. Where the container body is necked, the neck can be so shaped as to provide some measure of support and/or restraint for the carrier web around the hole in the latter, and to assist in locking the container to the web until the user wishes to pull it away from the carrier. Similarly, a reduced neck allows the cans to be held in close parallel relation thus, minimizing the total space needed to hold the containers. In addition, the necked end can can be designed to stack against the bottom of a similar container for ease of shipping.
Various method have been used and proposed for forming an end neck and flange on a one-piece can body. Some methods involve molding the neck and/or the flange by means of circumferentially extending molds. Die necking has also been used to longitudinally move a die against the end of a supported D&I can to force same to a smaller diameter by means of the application of the die. Other methods involve rolling or spinning the neck and/or flange, using an external spinning roll of a given shape co-operating with an internal member of a companion shape within the can body. In these latter methods, the can body is supported rigidly by an internal mandrel or the like; the internal member may be a spinning roll, pilot or it may be the mandrel which supports the can body. In one such method the neck and flange are formed simultaneously in a can body supported internally and rigidly by a mandrel or chuck of an expanding/collapsing type, the neck and flange profile being formed by external spinning rolls co-operating with this mandrel.
In another method, the can body is supported internally by an anvil and endwise by a spinning pilot, the neck and flange being formed by a profiled, external spinning roll which deforms the can body into a groove formed on the pilot and anvil, the roll being moved axially of the can body.
In all these previously-proposed methods the final profile of the neck and flange is determined by the set profiles of the tool elements used for forming them, in that the tool elements (i.e., spinning rolls, mandrels, anvil etc.) are provided rigidly with fix working surfaces shaped to conform with the ultimate shape of the neck and/or the flange, and the metal of the can body is deformed into conformity with these profiles. It is thus necessary, if a different shape is required to change the tools so as to provide differently profiled tool elements.
A method such as that mentioned above, in which an expanding mandrel is used enables end flanges and neck portions to be produced reliably and economically even on can bodies made in the thinner and harder metals currently in favor, in particular double-reduced plate which is usually tinplate, but which may, for example, be aluminum, mild steel or blackplate suitably treated but not necessarily plated with another metal. The present invention is also especially suitable for use with these thinner and harder double reduced or work hardened materials.
The problems with the rolling or spin forming of tooling used in the prior art concerns the weak and relatively unsupported upper sidewall metal of the open end of a D&I can body. Such metal is usually very thin around 0.004" to 0.006", highly worked during ironing and highly grain oriented. Merely placing a tool with the desired profile inside the container and applying a similarly shaped roller to the outside of the container while same is spun does not give the metal during the forming operation adequate or complete support to prevent wrinkling, cracking, buckling, crushing or tearing. This uncontrolled or unsupported application of radial side force on the thin metal sidewall of the open end is unacceptable particularly in connection with the higher temper (H19, T5 or double reduced) materials in connection with operations performed at high speeds wherein the rate of production of the containers during necking and flanging is more than several hundred per minute. No known method for providing adequate support or complete control of the metal during forming was known whereby the problems stated in connection with the forming of necked and flanged containers were overcome.